ros·tel·lum 
(rŏ-stĕləm)
(rŏ-stĕləm)n. pl. ros·tel·la (rŏ-stĕlə)
A small beaklike part, such as a projection on the stigma of an orchid or the hooked projection on the head of a tapeworm.
[Latin, diminutive of rōstrum, beak; see ROSTRUM.]
ros·tellar adj.